1. Field of the Invention
The present invention relates to an ophthalmic microscope, and more particularly, to an ophthalmic microscope provided with a laser photocoagulator with a system for ranging the focal point of the laser beam, and still further there is provided an improved binocular having microscopic magnification with erect, wide field, stereoscopic image viewing.
2. Description of the Prior Art
There are several laser photocoagulators used presently for cutting within the vitreous and for the purpose of fusing a detached retina. YAG lasers are also used for cutting strands or membranes which might develop in the pupil of the eye as well as in the vitreous cavity, that is, spaced from the fundus.
The problem with cutting strands in the vitreous cavity is that care must be taken to ensure the safety of the retina. For this purpose, the greatest possible aperture of beam is required which ensures the smallest possible focal spot with the shortest depth of focus of the laser beam.
The presently used system of a focal microscope which utilizes a plano concave contact lens, results in a diminished aperture angle. The pupil acts as a field stop and narrows the field for the observer. The alternative is to complicate the YAG beam delivery system to an extremely wide angle by space occupying devices on the slit lamp microscope that diminish the mobility of the device, or to use convex concave contact lenses that increase the beam aperture angle which compromises the field for the observer and further compromises stereopsis.
To overcome these difficulties, slit lamp illumination microscopy was described in the U.S. Pat. No. 4,307,944, Kurt Schirmer, issued Dec. 29, 1981. This patent described the use of an Argon laser photocoagulator but does not refer to the potential use of a YAG neodymium laser beam. The laser beam in the former patent came to a focus within the telescope. In the case of utilizing a YAG laser, the concept of focusing the laser beam within the telescope must be avoided.
Various erecting, stereoscopic binoculars are also known from the prior art. However, such prior art binoculars inevitably utilize hand-made expensive erecting prisms, such as roof top prisms.